The present invention relates to a high frequency heating apparatus having a steam generating function and more particularly to a technique for enhancing a cooking functionality and a heating efficiency.
Conventionally, there have variously been proposed a high frequency heating apparatus that supplies steam to a heating chamber accommodating a thing to be heated and heats the thing to be heated (for example, see Japanese Patent Publication JP-A-8-178298). The high frequency heating apparatus of this type can carry out cooking by properly combining high frequency heating, steam heating to be carried out by the supply of steam, and furthermore, heating to be performed by electric heating depending on the type of an apparatus.
In the high frequency heating apparatus, however, it takes a long time to reach a predetermined heating temperature after the supply of steam into a heating chamber at time of the start of heating. For this reason, a time required for cooking is prolonged and the device is not always easy to use. In order to quickly raise a temperature to a predetermined heating temperature, it is effective to increase the amount of generation of the steam. On the other hand, a dew condensation generated on a wall surface in the heating chamber is increased. Consequently, a large amount of water is stored in the bottom face of the heating chamber after the cooking and a great deal of time and labor is required for cleaning. Moreover, the steam supplied at a high temperature is condensed on the wall surface of the heating chamber. Thus, there is also a problem in that the heat quantity of the steam is taken away into the wall surface of the heating chamber so that the amount of heating for the thing to be heated is relatively decreased, resulting in a deterioration in the heating efficiency of the thing to be heated.
In a recent high frequency heating apparatus, furthermore, the volume of the heating chamber is increased so that a large-sized thing to be heated can be cooked. However, it is hard to raise the temperature of the whole heating chamber uniformly and quickly with an increase in the volume of the heating chamber. The shortage of a heating capability can be improved if the number of heating means and an output thereof are increased. However, this countermeasure is not preferable for a high frequency heating apparatus for an ordinary household in consideration of a reduction in a cost and energy saving.
In a conventional high frequency heating apparatus having a steam generating function, moreover, steam is only supplied into a heating chamber to cook a thing to be heated and there is no function of supplying the steam in a desirable timing during baking to regulate a baking condition, for example. Therefore, the cooking device does not make the most of the property of the steam during the cooking but utilizes the same property within a limited range.